1. Field of the Invention
The invention relates to demonstrating and testing in comparative manner the effectiveness of anti-reflection treatment of an ophthalmic lens.
2. Description of Related Art
There exists devices for measuring optical properties of an anti-reflection treatment by means of a system of the complex spectrometer type for measuring reflection. These optical properties are mean reflection Rm, visual reflection Rv, chrome C, and hue angle h.
There also exists a method of demonstrating the effectiveness of anti-reflection treatment in which the performance of a lens having anti-reflection treatment is compared with a lens not having such treatment, by means of right and left images that are reflected on right and left ophthalmic lenses worn by a wearer of an eyeglass frame in which one of the lenses has been subjected to anti-reflection treatment while the other has not been subjected to such treatment. The reflections of the images are viewed by the wearer when looking into a central mirror, or else by an observer. The wearer or the observer compares the difference in the anti-reflection effectiveness of the two lenses.
That type of method is not associated with any protocol and is therefore relatively inaccurate and random insofar as it depends on observation conditions.
Patent document US 2008/0124699 describes a demonstrator device having a part with a first face for supporting an image and a second face for supporting a mirror, which mirror is semi-reflective.
That device is for showing the effect of polarizing lenses or of lenses that are said to reduce polarized glare. Light is polarized naturally when a light ray is reflected with an angle of incidence equal to the Brewster angle on a surface that is plane, e.g. the ground or a sheet of water, and it becomes polarized linearly. Such lenses, by virtue of being polarized on a perpendicular axis, eliminate that reflected light or glare as perceived by the wearer of the lens.
According to that document, in the absence of polarizing lenses, the wearer sees firstly a first image that is not polarized and placed behind the mirror constituted by a semi-reflective film, and secondly a second image that is horizontally polarized after being reflected on the semi-reflective film. When the wearer views the demonstrator while using lenses that are polarized perpendicularly to the polarization axis of the second image, the polarizing filter effect of the lens enables the second image to be eliminated and the wearer sees only the first image.
That device, which is specifically adapted to testing polarizing lenses, cannot be used for testing the effectiveness of anti-reflection treatment that consists in attenuating reflections on the face of the lens visible from the outside by external people, and not by the wearer.